I’m Thinking of a Number

Choose a number between 1-100 but don’t tell your class what the number is. Now they must ask you questions to determine what the number is. But here is the catch…if they ask you a direct question, such as “Is the number 35?” they will be disqualified.

Students can eliminate half the numbers right away by asking if the number is odd or even or if it’s smaller or greater than 50.

They should be able to pinpoint the exact number in 7 questions or less.

Let’s say you chose the number 27.

Here are a series of questions that would work.

1) Is the number greater than 50? Your answer is no.
2) Is the number an odd number? Your answer is yes.
3) Is the number greater than 25? Your answer is yes.
4) Does the number have a digit of 3 in it? Your answer is no.
5) Does the number have a digit of 4 in it? Your answer is no.

So at this stage the only two numbers left are 27 and 29.

6) Does the number have a 9 in it? Your answer is no.

The answer is 27.

If you have a chart where you can remove the numbers as you’re going it will help students to narrow down the final number.